1. Technical Field
The present disclosure relates to the field of luminaires and, more particularly, to a retractable end-cap of a lighting tube.
2. Description of the Related Art
When a fluorescent tube lamp in a linear lighting fixture is retrofitted with a light-emitting diode (LED) tube, line voltage of 120V or 277V or higher is applied directly to the lamp-holders of the fixture and to the end-caps of the LED tube. If the LED tube employs double-end wiring, when one end of the LED tube connects with the power source, the other end of the LED tube instantly becomes live with electricity. This represents an electrical shock hazard for the installer of the LED tube.
One approach provides an LED tube wherein each of the two end-caps of the LED tube contains an extruded, spring-based safety switch. Before installation, the safety switch is not engaged and thus the bi-pins on the end-cap remain disconnected from the internal electric circuit of the LED tube. During installation, when one end-cap of the LED tube is inserted into the lamp-holder of a linear fixture, the external power source connects to the bi-pins on the end-cap, and at the same time the safety switch is pressed, thus connecting the bi-pins on the end-cap to the internal electric circuit of the LED tube. However, since the bi-pins of the remaining end-cap of the LED tube have not yet been inserted into the other lamp-holder on the linear fixture, the remaining safety switch is not engaged and therefore the remaining end-cap remains disconnected from both the external power source and the internal electric circuit of the LED tube. At this time, the installer can still safely touch the bi-pins of the disconnected end-cap with their bare hands without any risk of electrical shock. There are, however, two drawbacks with the inventive concept of the present disclosure. Firstly, when the lamp-holder loosens over time, the extruded, spring-based safety switch on the end-cap may not be properly engaged to connect the bi-pins to the internal circuit when the LED tube is installed into a linear fixture, resulting in poor connection between the LED tube and the external power source. Secondly, the length of the linear fixture varies. If an LED tube with the extruded, spring-based safety switch is inserted into a linear fixture that is slightly too long, the extruded, spring-based safety switch on the end-cap may not be properly engaged to connect the bi-pins to the internal circuit, resulting in poor connection between the LED tube and the external power source. If the linear fixture is shorter than the LED tube, it is not possible to insert the LED tube into the fixture.
Another approach provides an LED tube where a spring-based, floating end-cap is used on the LED tube. The bi-pins of the end-cap connect to the internal circuit of the LED tube. Before installation, the bi-pins are hidden inside the floating end-cap, and thus there is no risk of the installer making contact with the bi-pins. When the tube is inserted into a linear fixture, the spring-based, floating end-cap is pressed and retracts towards the center of the tube, thus exposing and enabling the bi-pins to connect to the external power source. This second approach solves the problem with the extruded, spring-based safety switch disclosed in the first approach mentioned above, where poor connection arises due to a loosened lamp-holder. However, this spring-based, floating end-cap design still does not solve the problem of differences in the length of the linear fixture, given the fact that the length of the LED tube with the floating end-caps is fixed. Moreover, the floating end-caps present another challenge; namely, the installer cannot see the bi-pins during installation because they are hidden inside the end-cap until the end-cap is pressed. As such, the installer needs to press both end-caps at the same time during installation to expose and insert the bi-pins into the lamp-holders. This is a very difficult task to perform when installing a 4-ft or 5-ft LED tube.